1. Field of the Invention
The invention relates to an electronic ballast and to an operating method for a gas discharge lamp, having a d.c. voltage converter, fed from a d.c. voltage source, with clocked switch and regulated output voltage, an inverter fed from the output d.c. voltage of the d.c. voltage converter, and a regulation circuit to which there is delivered a desired value signal and an actual value signal corresponding to the output d.c. voltage of the d.c. voltage converter, and which generates as setting value signal pulse width modulated switch-on pulses for the clocked switch.
2. Description of the Related Art
Such an electronic ballast is for example known from U.S. Pat. No. 5,705,897.
The d.c. voltage source for such an electronic ballast is normally a rectifier connected to the mains. The d.c. voltage converter then forms a PFC intermediate circuit (PFC=power factor correction), the task of which is to appear with respect to the mains as a quasi ohmic load. At the input of the d.c. voltage converter there lie the mains half-waves. The input current is formed by pulses the amplitudes of which likewise appear as sinusoidal half-waves. Between the half-waves of the input voltage of the input voltage and the half-waves formed by the amplitudes of the current pulses there is no phase displacement, so that a reactive loading of the mains is avoided and the generation of disruptive harmonics is reduced to a permissible level.
There are known different types of d.c. voltage converters which are for example described in the book by U. Tietze and Ch. Schenk “Semiconductor Circuit Techniques” (“Halbleiterschaltungstechnik”), publisher: Springer-Verlag, 1991, 9th Edition, pages 561–586. It is common to all that they include at least one clocked switch and at least two storage elements. For electronic ballasts there is mostly employed an upwards converter type, which—seen from the input to the output—consists of a charging choke in a first longitudinal branch, a clocked switch in a first transverse branch, a diode in a second longitudinal branch and a storage capacitor in a second transverse branch.
There has long been the tendency to produce electronic ballasts—as far as possible—using integrated circuit technology, i.e. as ASICs (application specific integrated circuits).